There are many types of topical antiperspirant products that are commercially available or otherwise known in the antiperspirant art. Most of these products are formulated as aerosol or pump sprays, roll-on liquids, creams, emulsions, gels, gel-solids, or other solid stick formulations, and comprise an astringent material, e.g. zirconium or aluminum salts or combinations thereof, incorporated into a suitable carrier. These products are designed to provide effective perspiration and odor control while also being cosmetically acceptable during and after application onto the axillary area or other areas of the skin.
Within this product group, solid anhydrous antiperspirant sticks have become especially popular among consumers. Most of these anhydrous sticks contain up to 80% by weight of a volatile silicone fluid such a cyclomethicone. The volatile silicone provides the composition with improved, drier skin feel during application, and because of its volatility, it quickly evaporates after application leaving the applied surface feeling smooth and dry. Volatile silicones are expensive, however, and add substantially to the cost of the finished product.
One attempt at reducing the cost of anhydrous antiperspirant sticks involves the use of volatile isoparaffins in place of some or all of the volatile silicones. Volatile isoparaffins are typically less expensive than the volatile silicone fluids, and like the volatile silicones, help provide the composition with dry feel during and after application to the skin. Examples of isoparaffin-containing compositions are described in U.S. Pat. No. 4,724,139, issued Feb. 9, 1988 to Palinczar, and U.S. Pat. No. 5,169,626, issued Dec. 8, 1992 to Tanner et al. The compositions described by Palinczar, however, after application to the skin tend to leave a relatively high visible residue, and tend to fracture upon application due to their inherently and relatively high elastic content.
It has now been found that a solid antiperspirant stick composition can be formulated which provides the dry skin feel and low-raw material cost of an isoparaffin-containing antiperspirant, with the low-residue performance and rheology of a gel-solid antiperspirant stick composition. This is accomplished by formulating an anhydrous system with from about 0.5% to about 60% by weight of an antiperspirant active; from about 1% to about 15% by weight of a gellant; from about 1% to about 50% by weight of a volatile nonpolar hydrocarbon solvent having a solubility parameter of less than 8 (cal/cm.sup.3).sup.0.5, a vapor pressure of from about 0.01 mmHg to about 6 mmHg at 25.degree. C. under one atomsphere, and an average boiling point of less than about 250.degree. C.; and from about 0.1% to about 10% by weight of polar, water-miscible, solvent having a solubility parameter of from 12.5 (cal/cm.sup.3).sup.0.5 to about 25 (cal/cm.sup.3).sup.0.5 ; wherein the composition has a visible residue index of from about 11 to about 30 L-value, a product hardness of from about 500 gram.cndot.force to about 5,000 gram force, a ratio of an elastic modulus (G') to a viscous modulus (G") of from about 0.1 to about 100.
It is therefore an object of the present invention to provide an anhydrous antiperspirant gel-solid stick composition which contains volatile, nonpolar hydrocarbon solvents such as volatile isoparaffins, and further to provide such a composition with improved low residue performance, rheology, efficacy, stability and/or aesthetics, and further to provide such a composition having reduced raw material costs.